Recent policy initiatives emphasize that encouraging marriage may help an effective strategy for improving the lives of economically disadvantaged single mothers and their children. Although decades of research establish that, on average, married individuals are healthier, happier, and less likely to live in poverty than their unmarried counterparts, there is a paucity of research examining the consequences of entering marriage for the health and well-being of single mothers, per se. The result is that we simply do not know if marriage is beneficial, neutral, or even harmful to single mothers'mental and physical health or that of their children. Although evidence that marriage improves the economic well-being of single mothers when it endures suggests optimism, we lack research that follows single mothers through a range of union transitions to assess their long term impact on health and well-being across the life course and across generations. Determining whether marriage is associated with better long-term outcomes for single mothers and their children is a crucial first step in assessing the likely success of marriage promotion initiatives. McLanahan summarizes the importance of this issue: "If parents marry, but children are worse off, such initiatives will have failed." Because more than 1/3 of all births in the U.S. occur to single mothers, identifying factors that improve or undermine the health and well-being of this vulnerable population has substantial relevance to public health. The central goal of the proposed project is to determine the consequences of single mother's union transitions (including marriage, cohabitation, and union dissolution) for their own health and well-being in mid-life and for the health, well-being and union formation patterns of their young adult offspring. Data for our study will come from the 1979 National Longitudinal Study of Young, an ongoing panel survey of a nationally representative sample of 12,686 young men and women who were aged 14-22 in 1979 and their offspring. Data currently span a 25-year period and the majority of children are now between the ages of 14 and 29. The aging of the NLSY79 cohort provides an unprecedented opportunity to investigate the intergenerational consequences of union transitions for the health and well-being of single mothers and their offspring.